Runaround coils

Runaround coils The coils in a heat recovery system that collect hear from the hot w aste steam and supply it to the cold incoming stream via heat exchangers. 

FIGURE 54.5 Heat recovery systems in dryers (a) thermal wheel (b) plate heat exchanger (c) heat pipe installation (d) runaround coil (e) scrubber and (f) two-section heat exchanger. 

As mentioned earlier, heat recovery from outlet vapors is a well-documented method for energy saving. In Figure 54.20, the application of two runaround coils in a spray dryer for dyes is shown schematically [78]. An important feature of this heat exchanger is the use of glass tubes from which it is easy to remove water-soluble dyes. The use of this system leads to a reduction in heat consumption by about 16% and annual savings of 4,500 GJ (i.e., 12,000). 

FIGURE 54.20 Schematic of two runaround coils in a spray dryer for dyes (1) spray dryer (2) exhaust heat exchanger (3) inlet heat exchanger (4) steam heater and (5) gas burner. (Courtesy of Energy Efficiency Office of the U. K. Department of Energy.)... 

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